Publicações

The creation of the General Transit Feed Specification (GTFS) in the mid-2000s provided a new data format for cities to organize and share digital information on their public transport systems. GTFS feeds store geolocated data on public transport networks, including information on routes, stops, timetables, and service levels. The GTFS standard is now widely adopted by thousands of transport authorities and a wide variety of software applications for different purposes, including trip planning, timetable creation and accessibility analysis. Yet, there is still a lack of tools to parse GTFS data when the objective is to analyze the complex spatial and temporal patterns of public transport systems. This paper presents {gtfs2gps}, a new general-purpose computational tool to easily process static GTFS data that allows one to analyze the spacetime trajectories of public transport vehicles at fine spatial and temporal resolutions. {gtfs2gps} is an open-source R package that employs parallel computing to convert GTFS feeds from relational text files into a trajectory data table, similar to GPS records, with the timestamps of vehicles in every trip. This paper explains the package functionalities and demonstrates how {gtfs2gps} can be used to articulate key concepts in time geography to explore and visualize the spatial and temporal patterns of public transport networks. We also present a case study looking at how {gtfs2gps} can be used to examine socioeconomic and spatialtemporal inequalities in access to public transport, providing key information to monitor cities progress toward the Sustainable Development Goals. The paper is accompanied by a computational notebook in R Markdown to support reproducibility of the results in this paper and to replicate the analysis for other contexts where GTFS data are available. Given the widespread use of GTFS, {gtfs2gps} opens new possibilities for researchers to examine the time geography of public transport systems in urban areas across the globe.

The Amazon Forest, the largest contiguous tropical forest in the world, stores a significant fraction of the carbon on land. Changes in climate and land use affect total carbon stocks, making it critical to continuously update and revise the best estimates for the region, particularly considering changes in forest dynamics. Forest inventory data cover only a tiny fraction of the Amazon region, and the coverage is not sufficient to ensure reliable data interpolation and validation. This paper presents a new forest above-ground biomass map for the Brazilian Amazon and the associated uncertainty both with a resolution of 250 meters and baseline for the satellite dataset the year of 2016 (i.e., the year of the satellite observation). A significant increase in data availability from forest inventories and remote sensing has enabled progress towards high-resolution biomass estimates. This work uses the largest airborne LiDAR database ever collected in the Amazon, mapping 360,000 km2 through transects distributed in all vegetation categories in the region. The map uses airborne laser scanning (ALS) data calibrated by field forest inventories that are extrapolated to the region using a machine learning approach with inputs from Synthetic Aperture Radar (PALSAR), vegetation indices obtained from the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite, and precipitation information from the Tropical Rainfall Measuring Mission (TRMM). A total of 174 field inventories geolocated using a Differential Global Positioning System (DGPS) were used to validate the biomass estimations. The experimental design allowed for a comprehensive representation of several vegetation types, producing an above-ground biomass map varying from a maximum value of 518 Mg ha-1, a mean of 174 Mg ha-1, and a standard deviation of 102 Mg ha-1. This unique dataset enabled a better representation of the regional distribution of the forest biomass and structure, providing further studies and critical information for decision-making concerning forest conservation, planning, carbon emissions estimate, and mechanisms for supporting carbon emissions reductions.

Studies of global carbon balance estimates are still incipient in the oceans of the Southern Hemisphere, mainly in coastal areas and continental shelf. Even in Brazil, despite its continental proportion coastline, there is still a great inconsistency in studies on the marine carbonate system and CO2 fluxes at the air-sea interface. This article presents a review of studies on CO2 fluxes on the coast of Brazil, published between the years 2000 and 2022, aiming to map the distribution of CO2 fluxes on the Brazilian continental shelf, to understand its role as a source or sink of CO2. In general, large-scale studies show that the Brazilian shelf exhibits a latitudinal variation of air-sea CO2 fluxes, behaving mainly as a source in the north, where there is no influence of the Amazon River plume, and as a sink in the south portion. We also identified there is a strong influence on the occurrence of mesoscale and synoptic oceanographic and meteorological events, and the presence of different ecosystems, which can change the behavior of CO2 fluxes locally. However, there are still many data gaps along the continental shelf, as well as in different seasons for the entire coast.

In hydrological modelling, it is important to consider the uncertainties related to a models structures and parameters when different hydrological models are used to represent a system. Therefore, an adequate analysis of daily discharge forecasts that takes into account the performance of hydrological models can assist in identifying the best extreme discharge forecasts. In this context, this study aims to evaluate the performance of three hydrological modelsLavras Simulation of Hydrology (LASH), Variable Infiltration Capacity (VIC), and Distributed Hydrological Model (MHD-INPE) in the Verde River basin. The results demonstrate that LASH and MHD can accurately simulate discharges, thereby establishing them as crucial tools for managing water resources in the study regions basins. Moreover, these findings could serve as a cornerstone for future studies focusing on food and water security, particularly when examining their connection to climate change scenarios.

Along with the accumulation of atmospheric greenhouse gases, particularly carbon dioxide, the loss of primary forests and other natural ecosystems is a major disruption of the Earth’s system and is causing global concern. Quantifying planetary warming from carbon emissions, global climate models highlight natural forests’ high carbon storage potential supporting conservation policies. However, some model outcomes effectively deprioritize conservation of boreal and temperate forests by suggesting that increased albedo upon deforestation could cool the planet. A potential conflict of global cooling vs. regional forest conservation could harm environmental policies. Here we present theoretical and observational evidence to demonstrate that, compared to the carbon-related warming, modeling skills for assessing climatic impacts of deforestation is low. We argue that estimates for deforestation-induced global cooling result from the models’ limited capacity to account for the global effect of cooling from evapotranspiration of intact forests. Specifically, transpiration of trees can change the greenhouse effect via small modifications of the vertical temperature profile. However, due to their convective parameterization (which postulates a certain critical temperature profile), global climate models do not properly capture this effect. This may lead to an underestimation of warming from the loss of forest evapotranspiration in both high and low latitudes. As a result, conclusions about deforestation-induced global cooling are not robust and could result in action that immediately worsened global warming. To avoid deepening the environmental crisis, these conclusions should not inform policies of vegetation cover management, especially as studies from multiple fields are accumulating that better quantify the stabilizing impact of natural ecosystems evolved to maintain environmental homeostasis. Given the critical state and our limited understanding of both climate and ecosystems, an optimal policy with immediate benefits would be a global moratorium on the exploitation of all natural forests.

While water lifting plays a recognized role in the global atmospheric power budget, estimates for this role in tropical cyclones vary from no effect to a major reduction in storm intensity. To better assess this impact, here we consider the work output of an infinitely narrow thermodynamic cycle with two streamlines connecting the top of the boundary layer in the vicinity of maximum wind (without assuming gradient-wind balance) to an arbitrary level in the inviscid free tropo-sphere. The reduction of a storm’s maximum wind speed due to water lifting is found to decline with increasing efficiency of the cycle and is about 5% for maximum observed Carnot efficiencies. In the steady-state cycle, there is an extra heat input associated with the warming of precipitating water. The corresponding positive extra work is of an opposite sign and several times smaller than that due to water lifting. We also estimate the gain of kinetic energy in the outflow region. Contrary to previous assessments, this term is found to be large when the outflow radius is small (comparable to the radius of maximum wind). Using our framework, we show that Emanuel’s maximum potential intensity (E-PI) corresponds to a cycle where total work equals work performed at the top of the boundary layer (net work in the free troposphere is zero). This con-strains a dependence between the outflow temperature and heat input at the point of maximum wind, but does not constrain the radial pressure gradient. We outline the implications of the established patterns for assessing real storms.

As mudanças no clima global resultado da emissão efeito estufa (GEE), estão cada vez mais perceptíveis em todas as atividades humanas. Na América do Sul (AS) as mudanças climáticas são potencializadas por efeitos concomitantes tais como alterações na cobertura da terra, por exemplo o desmatamento da floresta Amazônica e o efeito do CO2 na floresta. Conversões das áreas de floresta, seja por pasto ou áreas agricultáveis, trazem significativas mudanças no balanço de radiação, energia e água. O objetivo geral deste trabalho consiste em avaliar o impacto do desmatamento da Amazônia adjunto ao aumento médio da temperatura global em 2º C no clima das bacias Amazônica, São Francisco e Plata. Através de um estudo de modelagem foi possível a identificação dos principais efeitos e interações no sistema biosferaatmosfera. O Brazilian Atmospheric Model (BAM) e Community Earth System Model (CESM) forçados por diferentes condições de Temperatura da Superfície do Mar (TSM) dos conjuntos Coupled Model Intercomparison Project 5 and 6 (CMIP5 e CMIP6) foram escolhidos para avaliar as alterações atmosféricas e o modelo Potential Vegeation Model versão 2 (CPTEC-PVM2) foi utilizado para avaliar os biomas potenciais. O estudo considerou o cenário de emissões Representative Concentration Pathways (RCP8.5) além da configuração original da Floresta Amazônica (00DEF) e a conversão total da área de Floresta Tropical em pasto (100DEF), e o desmatamento de todas as florestas tropicais do globo (100WDEF). O índice Global Warming Level (GWL) foi escolhido para avaliar as simulações. As avaliações dos impactos foram direcionadas para o Specific Warming Level 2 (SWL2) na tentativa de responder como o desmatamento da Amazônia ou das florestas tropicais poderiam contribuir para um adiantamento do SWL2. Os resultados indicaram um adiantamento médio SWL2 em 2 anos (CPTEC-BAM) e 3 anos (CESM) entre os cenários 00 e 100DEF. Algumas regiões na AS, em especial norte, nordeste e centro, registraram um aquecimento médio anual entre 1º até 6º C. O enfraquecimento do ciclo hidrológico na bacia Amazônica ocorreu desde o cenário 00DEF em razão da influência das concentrações de CO2 atmosférico na condutância estomática (redução). Ainda, houve diminuição do fluxo de calor latente calor latente (~ -15 W/m2), aumento do calor sensível (~ +10 W/m2), diminuição da precipitação (~ – 1,5 mm.dia-1) e diminuição da evapotranspiração (ET) em toda área da floresta Amazônica (~ -0,5 mm.dia-1). O cenário 100DEF indicou impactos severos no clima regional através da redução do transporte de umidade para o Sudeste do Brasil (~ -15%) e aumento no sul da bacia La Plata (+20%). Enquanto o modelo BAM mostrou-se mais sensível ao aquecimento global, aumentando o aporte de umidade específica na atmosfera, o modelo CESM mostrou-se sensível as alterações da vegetação, indicando reduções drásticas da umidade específica sob a floresta. Por fim, ocorreu redução do índice CAPE ao norte da bacia La Plata (100DEF) e no Alto São Francisco. O modelo CPTEC-PVM2 indicou redução da área de floresta tropical na bacia Amazônica contrastando com aumento das áreas de savana e floresta tropical sazonal, o qual tornou-se mais extrema para os inputs com o modelo CESM. Reflexo esse da maior intensidade da redução da precipitação e aumento da temperatura e, com o fortalecimento dos ventos alísios, o maior aporte de umidade foi redirecionado para o extremo oeste da bacia Amazônica. Isso refletiu na maior disposição do bioma floresta Tropical nessa área. O desmatamento quando considerado concomitantemente ao aquecimento global pode aumentar a intensidade das alterações ou indicar um diferente comportamento das condições atmosféricas.

The increase in greenhouse gasses (GHG) anthropogenic emissions and deforestation over the last decades have led to many chemical and physical changes in the climate system, affecting the atmosphere’s energy and water balance. A process that could be affected is the Amazonian moisture transport in the South American continent (including La Plata basin), which is crucial to the southeast Brazilian water regime. The focus of our research is on evaluating how local (i.e. Amazon deforestation) and global forcings (increase of atmospheric GHG concentration) may modify this moisture transport under climate change scenarios. We used two coupled land-atmosphere models forced by CMIP6 sea surface temperatures to simulate these processes for two scenarios: i) increase in carbon dioxide (CO2) RCP8.5 atmospheric levels (00DEF), and ii) total Amazon deforestation simultaneous with atmospheric CO2 levels increased (100DEF). These scenarios were compared with a control simulation, set with a constant CO2 of 388 ppm and present-day Amazon Forest cover. The 30-year Specific Warming Level 2 (SWL2) index evaluated from the simulations is set to be reached 2 years earlier due to Amazon deforestation. A reduction in precipitation was observed in the Amazon basin (−3.1 mm·day−1) as well as in La Plata Basin (−0.5 mm·day−1) due to reductions in the Amazon evapotranspiration (−0.9 mm·day−1) through a stomatal conductance decrease (00DEF) and land cover change (100DEF). In addition, the income moisture transport decreased (22 %) in the northern La Plata basin in both scenarios and model experiments. Our results indicated a worse scenario than previously found in the region. Both Amazon and La Plata hydrological regimes are connected (moisture and energy transport), indicating that a large-scale Amazon deforestation will have additional climate, economic and social implications for South America.

Projections of future carbon sinks and stocks are important because they show how the world’s ecosystems will respond to elevated CO2 and changes in climate. Moreover, they are crucial to inform policy decisions around emissions reductions to stay within the global warming levels identified by the Paris Agreement. However, Earth System Models from the 6th Coupled Model Intercomparison Project (CMIP6) show substantial spread in future projectionsespecially of the terrestrial carbon cycle, leading to a large uncertainty in our knowledge of any remaining carbon budget (RCB). Here we evaluate the global terrestrial carbon cycle projections on a region-by-region basis and compare the global models with regional assessments made by the REgional Carbon Cycle Assessment and Processes, Phase 2 activity. Results show that for each region, the CMIP6 multi-model mean is generally consistent with the regional assessment, but substantial cross-model spread exists. Nonetheless, all models perform well in some regions and no region is without some well performing models. This gives confidence that the CMIP6 models can be used to look at future changes in carbon stocks on a regional basis with appropriate model assessment and benchmarking. We find that most regions of the world remain cumulative net sources of CO2 between now and 2100 when considering the balance of fossil-fuels and natural sinks, even under aggressive mitigation scenarios. This paper identifies strengths and weaknesses for each model in terms of its performance over a particular region including how process representation might impact those results and sets the agenda for applying stricter constraints at regional scales to reduce the uncertainty in global projections.

Anthropogenic disturbances directly influence environmental processes and increase the concentration of carbon (C) in the atmosphere. Here, we compare the differences in the seasonality of the balance of carbon, energy, and radiation, as well as seek to identify the interrelationships between these environmental variables and their impact on the growth of Opuntia cactus. Data were acquired from an eddy covariance flux tower over a cactus crop agroecosystem (2019-2021) in the Brazilian semi-arid region. In addition, we use plant growth rates, carbon and nutrient stocks, evapotranspiration (ET) and water use efficiency (WUE), and radiation (RUE). We show that the closure of the surface energy balance was 71%, although there are minimal fluxes of available energy lost (29%) by unquantified processes. At all seasons, the highest net ecosystem CO2 exchange (NEE) rate was between 11:00-13:00 (-5.75 mu mol m- 2 s- 1). During the dry and wet-dry season, there was the lowest daily gross primary productivity (GPP) (2.5 mu mol m- 2 s- 1) and net radiation-Rn (217.97 W m-2). Ecosystem respi-ration was more expressive during the wet season (2.41 mu mol m- 2 s- 1), and maximum diurnal value of 2.65 mu mol m- 2 s- 1. Furthermore, the latent heat flux was higher during the wet season (114.68 W m-2) and lowered in the dry season (9.39 W m-2). The net assimilation rate showed higher values during the dry-wet transition. The dry season presented higher nutrient use efficiency and WUE (14.77 g m- 2 mm -1). The highest ET occurred during the wet season (227 mm), and RUE was 81.48% higher than in the dry season. Overall, the cactus was a potential C sink during the three years of assessment (NEE:-377 g C m- 2 year- 1; GPP: 881 g C m- 2 year- 1). The results help us to understand that most of the Rn energy is used in the sensible heat flux (58% ratio).

Investigamos o efeito de eventos de sobreirradiância em inversores para diferentes tecnologias de módulos (CdTe, CdTe ARC, mc-Si), buscando indícios de perda de potência DC/AC e correntes DC capazes de causar efeitos deletérios nos fusíveis dos sistemas em estudo. Analisamos uma série de dados de três anos de medições de irradiância solar e produção fotovoltaica, registrados em um sistema experimental localizado no laboratório FOTOVOLTAICA UFSC, Florianópolis, Brasil. Identificamos e caracterizamos eventos de sobreirradiância solar (OIEs) e eventos de sobreirradiância solar extremos (EOIEs). Foram analisadas as variáveis de entrada e de saída em inversores fotovoltaicos durante tais eventos. Foi evidenciada variabilidade na composição espectral de EOIEs. Na localidade estudada, não foram detectados eventos com duração maior de 1 minuto capazes de causar clipping de inversor ou efeitos deletérios, porém em diversas ocasiões foram observados eventos limítrofes.

Here we analyze the trends of rainfall and the frequency of rainy days over the Brazilian Cerrado between 1960 and 2021 in four distinct periods according to the seasonal patterns over the region. We also evaluated trends in evapotranspiration, atmospheric pressure, winds, and atmospheric humidity over the Cerrado to elucidate the possible reasons for the detected trends. We recorded a significant reduction in rainfall and frequency of rainy days in the northern and central Cerrado regions for all periods except at the beginning of the dry season. The most pronounced negative trends were recorded during the dry season and the beginning of the wet season, where we recorded reductions of up to 50% in total rainfall and the number of rainy days. These findings are associated with the intensification of the South Atlantic Subtropical Anticyclone, which has been shifting atmospheric circulation and raising regional subsidence. Moreover, during the dry season and the beginning of the wet season, there was a reduction in regional evapotranspiration, which also potentially contributed to the rainfall reduction. Our results suggest an expansion and intensification of the dry season in the region, potentially bringing broad environmental and social impacts that transcend the Cerrado boundaries.